Silo safety system

ABSTRACT

The silo safety system implements safety logic for silo opening gates by utilizing light sensors connected to a programmable logic controller or equivalent configuration of relay contact switches. Photodetection sensors and their associated light transmitters are placed on opposing lateral sides along a truck passageway under the silos where the tail, middle, and front of a truck are presupposed to be. When a truck pulls under the silos, system logic uses the resultant pattern of beam breaks to prevent the silo gates from opening unless the truck cab is clear from the silo that the truck is supposed to be under. For two or more silos, the system enables only the correct silo, while the other silos are disabled. The silo that the truck is under can then only be energized by the silo control operator. The control logic can have a default configuration for a predetermined truck size.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/202,026, filed Jan. 21, 2009.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to safety systems. More specifically, the present invention relates to a silo safety system for releasing overhead silo contents only under the load-receiving portion of a truck.

2. Description of the Related Art

In a modern asphalt production facility large quantities of asphalt are loaded into huge silos, which can contain several tons of hot asphalt. In general, several of these silos are set up in line to hold a large batch of asphalt. Due to the massive quantities of asphalt needed for installing a road, many silos will exist in a single row. In general, the silos are spaced close together to reduce heat loss. The silos are all elevated a significant distance above the ground in order that a truck to be able to pull underneath them. Once a truck is pulled underneath the proper silo, a hatch is opened and the hot asphalt is loaded into the back of the dump truck. The dump truck then proceeds to transport the hot asphalt to the location where the road is being installed. The hot asphalt is unloaded from the dump truck into a spreader, which will deposit asphalt across a single lane of a highway at a uniform depth. The hot asphalt is then anchored in place or compressed through the use of a steamroller. Once the asphalt is cooled it becomes a hard surface upon which automobiles and trucks may travel smoothly.

When the asphalt is being loaded from the silo into the dump truck, the dump truck pulls up with its bed directly below the hatch for the silo. Once the truck is in position, the hatch opens and several tons of hot asphalt come streaming into the bed of the truck. In general, the driver will remain seated in the truck during the loading operation to reduce the total loading time. It is essential that the asphalt be transported to the location at which the road is being built in a short period of time. Although the asphalt will remain hot for several hours, it must be place in the spreader and rolled before it cools in order to provide a strong, hard surface upon which traffic may travel. Cool or cold asphalt does not bind together very well and will deteriorate and result in potholes in the smooth surface. As a result, asphalt truckloads that arrive with the load having a temperature below the minimum acceptable are sent back for reheating or recycling.

As a result, a dump truck arrives at the plant, quickly pulls under the silos, is loaded with asphalt and the truck departs. During the loading process, the driver stops only to place or confirm the order, to have the truck loaded and to have paperwork processed. The entire loading process is done as quickly as possible to have the asphalt arrive at the work site within preparation temperature limits. In order to reduce heat loss while the asphalt is sitting in the silo, the silos are generally constructed to have a greater height than surface width. Since heat rises, a smaller surface area will allow less heat to escape. Accordingly, the silos are placed close together so that minimal heat is lost through the sides. This procedure results in the silos being spaced apart approximately one-half dump truck length. It should be readily understood that while a dump truck is positioned such that the center of its bed is underneath one silo hatch, the cab of the truck will be located approximately beneath the hatch of another silo.

The aforementioned situation provides a very real degree of danger to the truck driver. Although millions of dump trucks have been loaded with hot asphalt since the beginning of its use for roads without incident, a significant number of trucks have been inadvertently buried and truck operators sent to the hospital due to resulting injury from being dumped on. For example, the unloading of several tons of hot asphalt on the cab of a truck can result in severe burns to the driver. It is imperative that steps be taken to prevent such a mishap.

Thus, a silo safety system solving the aforementioned problems is desired.

SUMMARY OF THE INVENTION

The silo safety system implements safety logic for silo opening gates by utilizing light sensors operably connected to a programmable logic controller or an equivalent logical configuration of relay contact switches. Photo detection sensors and their associated light transmitters are placed on opposing lateral sides along a truck passageway under the silos where the tail, middle, and front of a truck are presupposed to be.

When a truck pulls under the silos, the beams sent by the transmitters are broken at various locations along the passageway. System logic reads the pattern of beam breaks and based on said beam break pattern prevents the silo gates from opening unless the truck cab is clear from the silo that the truck is supposed to be under.

If two or more silos are involved, the system utilizes the beam break pattern to enable only the correct silo while disabling the other silos. The silo that the truck is under can then only be energized by the silo control operator. The control logic can be configured according to the size of truck entering the silo passageway. A default configuration can be specified for a particular class size of vehicles.

These and other features of the present invention will become readily apparent upon further review of the following specification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an environmental, perspective view of an exemplary silo safety system according to the present invention.

FIG. 2A is a schematic diagram of an exemplary silo safety system according to the present invention, showing the arrangement of switch contacts in relation to the sensors and the silos.

FIG. 2B is a schematic diagram of insert points for the silo safety system of FIG. 2A.

Similar reference characters denote corresponding features consistently throughout the attached drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The silo safety system implements safety logic for silo opening gates by utilizing light sensors operably connected to a programmable logic controller (PLC) or an equivalent logical configuration of relay contact switches. Photo detection sensors and their associated light transmitters are placed on opposing lateral sides along a truck passageway under the silos where the tail, middle, and front of a truck are presupposed to be.

Referring to FIG. 1, a typical silo structure 5 comprising silos 6 a and 6 b is supported by horizontally disposed support members connected to left side vertical support members 7 i and right side vertical support members 7 r. Beam transmitters TX are disposed in the left side vertical supports 7 i. Corresponding beam receivers RX are disposed in the right side vertical supports 7 r. When a truck T pulls under the silos, the beams sent by the transmitters TX to receivers RX are broken at locations determined by longitudinal spacing of successive pairs of vertical supports 7 i, 7 r along the passageway under silos 6 a and 6 b.

FIGS. 2A and 2B illustrate logic principles of the silo safety system utilizing a combination of pictorial blocks in conjunction with conventional ladder logic diagrammatic nomenclature according to the industrial automation standards embodied in Programmable Controllers Standard International Electrotechnical Commission (IEC) 61131-3. A ladder diagram according to the aforementioned standard may be incorporated to illustrate logical design. For example the logical design of C=A and NOT B can be represented as a Ladder Diagram (LD) rung accordingly:

Light emitting transmitters 50 a and associated photodetection sensors 52 a, shown in FIG. 2A, can be utilized as the transmitters TX and receivers RX in the system of FIG. 1. As most clearly shown in FIG. 2A, there are three transmitter-receiver pairs (50 a-52 a, 50 b-52 b, 50 c-52 c) associated with first silo, Silo 1, the transmitter-receiver pairs being longitudinally separated from each other by a predetermined distance. Similarly, there are three longitudinally separated transmitter-receiver pairs (50 d-52 d, 50 e-52 e, 50 f-52 f) associated with second silo, Silo 2, and three longitudinally separated transmitter-receiver pairs (50 g-52 g, 50 h-52 h, 50 i-52 i) associated with third silo, Silo 3.

FIG. 2B shows preexisting ladder diagram (LD) rungs 20 for energizing silo gate solenoid SG1 to open Silo1, SG2 to open Silo2 and SG3 to open Silo 3, respectively. The control circuitry of FIG. 2 a is inserted at cut points 21, 22, and 23 to form the silo safety system. Without the silo safety system 10 inserted at cut points 21, 22, and 23, a silo operator could energize normally open switch R4 to close SG1, energize normally open switch R8 to close SG2, or energize normally open switch R12 to close SG3. All solenoid gates could be opened without regard to safe positioning of a truck's cab or load receiving portion. As shown in FIGS. 2A-2B, during normal operations with an open silo control panel bypass switch 54 a, the R4 rung to operate silo safety gate SG1 is actuable only if (R1 AND R3 AND R2) AND (NOT R8) AND (NOT R12). Referring to rungs R8 and R12 in FIG. 2B, it is readily apparent that the negation of R8, i.e., (NOT R8) and the negation of R12, i.e., (NOT R12) require that silo operator deactivate switches R8 and R12 controlling SG2 and SG3. Switches R5, R7, R6, R9, R11, and R10 switches are required to be in the same state as R1, R3, R2, i.e., their state being closed when beams between transmitters 50 a through 50 i and receivers 52 a through 52 i are broken by a portion of a vehicle under the silos.

Similarly, the R8 rung to operate silo safety gate SG2 is actuable only if (R5 AND R7 AND R6) AND (NOT R4) AND (NOT R12). Referring now to rungs R4 and R12 in FIG. 2B, it is readily apparent that the negation of R4, i.e., (NOT R4) and the negation of R12, i.e., (NOT R12) require that the silo operator deactivate switches R4 and R12 controlling SG1 and SG3. Switches R1, R3, R2, R9, R11, and R10 are required to be in the same state as R5, R7, R6, i.e., their state being closed when beams between transmitters 50 a through 50 i and receivers 52 a through 52 i are broken by a portion of a vehicle under the silos.

The logic is similar for R12 rung to operate silo safety gate SG3, being actuable only if (R9 AND R11 AND R10) AND (NOT R4) AND (NOT R8). Referring now to rungs R4 and R8 in FIG. 2B, it is readily apparent that the negation of R4, i.e., (NOT R4) and the negation of R8, i.e., (NOT R8) require that silo operator deactivate switches R4 and R8 controlling SG1 and SG2. Switches R1, R3, R2, R5, R7, and R6 are required to be in the same state as R9, R10, R11, i.e., their state being closed when beams between transmitters 50 a through 50 i and receivers 52 a through 52 i are broken by a portion of a vehicle under the silos.

The control logic can be configured according to the size of the trucks entering the silo passageway. A default configuration can be specified for a particular class size of vehicles. Normally closed transmitter bypass switches 48 a, 48 b and 48 c, preferably being mounted on vertical support structure 7 i, can cut off the beams directed to corresponding receivers on opposing support structure 7 r. For example, if a load receiving portion of a truck is located under Silo 3, but no portion of the vehicle is under Silo 1 or Silo 2, then the truck operator can open bypass switches 48 a and 48 b to power down transmitters 50 a through 50 f, thereby enabling the aforementioned control logic to allow the silo operator to close R12 in order to deposit the Silo 3 load into a load receiving portion of the truck.

Bypass buttons, e.g., normally open electrical switches 54 a through 54 c, are preferably located in a silo control panel and are capable of bypassing logic switches R1, R3, or logic switches R5, R7, or logic switches R9, R11, respectively, depending on the positioning of a smaller vehicle under the silos. When a bypass button is closed, a smaller vehicle need only break one of the transmission beams associated with a particular silo.

It is to be understood that the present invention is not limited to the embodiment described above, but encompasses any and all embodiments within the scope of the following claims. 

1. A silo safety system, comprising: at least one transmitter-detector pair positioned for detecting presence of a vehicle in a passageway of at least one silo; and a control logic device connected to the detector of the at least one transmitter-detector pair, the control logic device being configured for identifying whether the at least one silo can be unloaded based upon the position of the vehicle in the passageway.
 2. The silo safety system according to claim 1, wherein said at least one transmitter-detector pair comprises a transmitter disposed on a first lateral side of the passageway under the at least one silo and a receiver disposed on a second opposing lateral side of the passageway under the at least one silo.
 3. The silo safety system according to claim 2, wherein said at least one transmitter-detector pair comprises a plurality of transmitter-detector pairs disposed at predetermined intervals along a length of the passageway under the at least one silo.
 4. The silo safety system according to claim 1, wherein said transmitter comprises a photo beam emitter and said detector comprises a photo beam detector.
 5. The silo safety system according to claim 1, wherein said control logic device is adapted for connection to pre-existing silo control circuitry at predetermined cut-points.
 6. The silo safety system according to claim 1, wherein the control logic device comprises a programmable logic controller adapted for operable communication with silo gate opening solenoids, said control logic device preventing actuation of the silo gate opening solenoids until the vehicle position has been verified by said at least one transmitter-detector pair to be in a correct vehicle position with respect to location of at least one silo.
 7. The silo safety system according to claim 1, further comprising a plurality of transmitter bypass switches accessible to a silo operator, the transmitter bypass switches being configurable by the silo operator to disable said at least one transmitter-detector pair, thereby allowing the silo operator to unload the at least one silo for smaller vehicles undetectable by said at least one transmitter-detector pair.
 8. The silo safety system according to claim 1, wherein the control logic device has a default configuration for a predetermined truck size.
 9. The silo safety system according to claim 1, wherein said at least one transmitter-detector pair has an output providing a Boolean logical expression used by said control logic device to identify whether the at least one silo can be unloaded based upon the position of the vehicle in the passageway. 